$ mvn -pl order-fulfillment -am test -Dtest=ModularityTests#verifiesModuleStructure
(captured with OrderManagement depending on InventoryManagement -- inventory's actual
 public API, not an internal type -- expecting this to fix the earlier violation)

org.springframework.modulith.core.Violations: - Cycle detected: Slice inventory ->
                Slice order ->
                Slice inventory
  1. Dependencies of Slice inventory
    - Method <com.ankurm.modulithdemo.inventory.InventoryManagement.on(com.ankurm.modulithdemo.order.OrderPlaced)> has parameter of type <com.ankurm.modulithdemo.order.OrderPlaced> in (InventoryManagement.java:0)
    - Method <com.ankurm.modulithdemo.inventory.InventoryManagement.on(com.ankurm.modulithdemo.order.OrderPlaced)> calls method <com.ankurm.modulithdemo.order.OrderPlaced.sku()> in (InventoryManagement.java:44)
    - Method <com.ankurm.modulithdemo.inventory.InventoryManagement.on(com.ankurm.modulithdemo.order.OrderPlaced)> calls method <com.ankurm.modulithdemo.order.OrderPlaced.quantity()> in (InventoryManagement.java:45)
    - Method <com.ankurm.modulithdemo.inventory.InventoryManagement.on(com.ankurm.modulithdemo.order.OrderPlaced)> calls method <com.ankurm.modulithdemo.order.OrderPlaced.orderId()> in (InventoryManagement.java:48)
    - Method <com.ankurm.modulithdemo.inventory.InventoryManagement.on(com.ankurm.modulithdemo.order.OrderPlaced)> calls method <com.ankurm.modulithdemo.order.OrderPlaced.sku()> in (InventoryManagement.java:48)
  2. Dependencies of Slice order
    - Constructor <com.ankurm.modulithdemo.order.OrderManagement.<init>(com.ankurm.modulithdemo.order.internal.OrderRepository, org.springframework.context.ApplicationEventPublisher, com.ankurm.modulithdemo.inventory.InventoryManagement)> has parameter of type <com.ankurm.modulithdemo.inventory.InventoryManagement> in (OrderManagement.java:0)
    - Field <com.ankurm.modulithdemo.order.OrderManagement.inventory> has type <com.ankurm.modulithdemo.inventory.InventoryManagement> in (OrderManagement.java:0)
    - Method <com.ankurm.modulithdemo.order.OrderManagement.placeOrder(java.lang.String, int)> calls method <com.ankurm.modulithdemo.inventory.InventoryManagement.isInStock(java.lang.String, int)> in (OrderManagement.java:40)

Tests run: 1, Failures: 0, Errors: 1, Skipped: 0 -- BUILD FAILURE

Notice: no "non-exposed type" complaint this time -- InventoryManagement is inventory's
real public API, exactly as advertised. Only "Cycle detected" remains, which proves the
point: going through the public API fixes visibility violations, not direction
violations. inventory already depends on order (its listener takes OrderPlaced as a
parameter), so order depending on inventory in return -- through any type, public or
not -- closes a cycle. The fix is to remove the dependency, not to launder it.